Photoproduction of H(2) gas was examined in the Chlamydomonas reinhardtii tla1 strain, CC-4169, containing a truncated light-harvesting antenna, along with its parental CC-425 strain. Although enhanced photosynthetic performance of truncated antenna algae has been demonstrated previously (Polle etal. Planta 2003; 217:49-59), improved H(2) photoproduction has yet to be reported. Preliminary experiments showed that sulfur-deprived, suspension cultures of the tla1 mutant could not establish anaerobiosis in a photobioreactor, and thus, could not photoproduce H(2) gas under conditions typical for the sulfur-deprived wild-type cells (Kosourov et al. Biotech Bioeng 2002; 78:731-40). However, they did produce H(2) gas when deprived of sulfur and phosphorus after immobilization within thin (similar to 300 mu m) alginate films. These films were monitored for long-term H(2) photoproduction activity under light intensities ranging from 19 to 350 mu E m(-2) s(-1) PAR. Both the tla1 mutant and the CC-425 parental strain produced H(2) gas for over 250 h under all light conditions tested. Relative to the parental strain, the CC-4169 mutant had lower maximum specific rates of H(2) production at low and medium light intensities (19 and 184 mu E m(-2) s(-1)), but it exhibited a 4-times higher maximum specific rate at 285 mu E m(-2) s(-1) and an 8.5-times higher rate at 350 mu E M(-2) s(-1) when immobilized at approximately the same cell density as the parental strain. As a result, the CC-4169 strain accumulated almost 4-times more H(2) than CC-425 at 285 mu E M(-2) s(-1) and over 6-times more at 350 mu E M(-2) s(-1) during 250-h experiments. These results are the first demonstration that truncating light-harvesting antennae in algal cells can increase the efficiency of H(2) photoproduction in mass culture at high light intensity. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.